Arrangement of a heating unit in reaction apparatus

ABSTRACT

A reaction vessel, for carrying out thermal reactions, has a heat exchange medium circulated therethrough and through a cooler connected to the vessel. A heating unit is provided, external to the reaction vessel, and is connected to the reaction vessel at two points at different respective pressures, for parallel connection of the heating unit with the normal circulating system of the heat carrier for selective circulation of a regulated at least partial current of the heat carrier through the heating unit. The heating unit may be fluid heated or may be electrically heated, and control and shut-off valve means are provided whereby the heating unit may be selectively placed into operation or cut out of operation. The heating unit also may readily be removed from the reaction vessel.

United States Patent Gutlhuber l l Oct. 2, 1973 I54] ARRANGEMENT OF A HEATING UNIT IN 3,609,296 9/1971 Blair 165/1117 X 3,662,817 5 1972 Kendrick Cl 111. H 165/145 REACTION APPARATUS [75] Inventor: g z f g g Primary ExaminerManuel A. Antonakas u manns 6 ermany Atl0rneyJohn J. McGlew ct al. [73] Assignee: Deggendorfer Werft und Eisenbau G.m.b.H., Deggendorf/Donau, 57] ABSTRACT Germany A react1on vessel, for carrymg out thermal react1ons, [22] Filed: Dec. 13, 1971 has a heat exchange medium circulated therethrough and through a cooler connected to the vessel. A heating [2111 Appl' 207399 unit is provided, external to the reaction vessel, and is connected to the reaction vessel at two points at differ- [30] Foreign Application Priority Data ent respective pressures, for parallel connection of the Dec. 17, 1970 Germany P 20 62 09515 heating unit with the normal Circulating System Of the heat carrier for selective circulation of a regulated at 52 US. Cl. 165/107, 165/159 least Partial current of the heat Carrier through the 511 Im. c1 F28f 9/22 heating unit The heating unit y be fluid heated or [58] Field of Search 165/107, 159, 145 y be electrically heated, and eentrel and Shut-eff valve means are provided whereby the heating unit may 5 References Cited be selectively placed into operation or cutout ofopera- UNITED STATES PATENTS tion. The heating unit also may readily be removed from the reaction vessel. 3,434,807 3/1969 lblng et al 165/159 X 3,566,961 3/1971 Lorenz 165/107 X 5 Claims, 4 Drawing Figures t I I, 1 7 U 1 /J" g I I 17 l 17 I I i t I T r z/ 1 i I I ,1

PATENIED 3.762.465

INVENTOR.

ARRANGEMENT OF A HEATING UNIT IN REACTION APPARATUS FIELD OF THE INVENTION This invention relates to reaction apparatus in which thermal reactions are carried out in a vessel by circulation of a heating medium through the vessel and through a cooler, and, more particularly, to a novel and improved external heating unit for such a vessel.

BACKGROUND OF THE INVENTION In reaction apparatus with which thermal reactions are carried out, the heat exchange medium generally is circulated by means of a pump, in order to maintain a substantially constant operating temperature, generally between 350 and 450 C, and the heat generated during the reaction process is transferred to a cooler arranged in the circulation circuit.

Such a system occasionally must be shut-off and subsequently restarted, for example when replacing the catalyst. After the restarting, the reaction process sets in again only after there has been attained a higher temperature than existed before the system was shutdown. Consequently, a corresponding preheating of the reaction vessel is necessary. This can be attained by using an additional heat carrier which is conducted through the reaction chamber. However, steam of a sufficiently high temperature is hardly available, while hot air and flue gas require a considerable expenditure for heating units and accessories and result in operating losses.

There are also known heating units which are installed in the reaction vessel and act therein on the heat exchange medium. However, such units are limited in size and thus also in their heating capacity. In addition, such installations effect a steady pressure loss in the operation of the plant, so that the circulating pump for the heat exchange medium must be made correspondingly more powerful. In addition, the entire plant must be shut-off for each check or repair, even if the operation of the heating unit is not necessary at the respective time.

SUMMARY OF THE INVENTION The invention is based on a known arrangement wherein the heating unit, for the heat exchange medium circulating in a reaction vessel, is outside the re action vessel. The novel and special feature of the invention resides in that the heating unit is connected to the reaction vessel at two points, at respective different pressures, in parallel connection to the regular circulating system of the heat exchange medium, for the intermittent passage of a preferably adjustable partial current of the heat exchange medium.

In accordance with another feature of the invention, the heating unit can be connected to the reaction vessel at the inlet side or the outlet side through a combination shut-off and control element.

An object of the invention is to provide an improved arrangement for preheating a reaction vessel.

Another object of the invention is to provide such an arrangement in which a heating unit is arranged outside the reaction vessel and connected thereto for selective circulation, through the heating unit, of at least a part of the heat exchange medium.

A further object of the invention is to provide such an arrangement in which the heating unit is connected to the reaction vessel at two points at respective different pressures and in parallel relation to the regular circulating system of the heat exchange medium.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a longitudinal section through a reaction vessel with outside units for cooling or heating the circulating heat exchange medium;

FIG. 2 is a cross-sectional view taken on the line IIII of FIG. 1;

FIG. 3 is a view similar to FIG. 1 illustrating another embodiment of the invention wherein only the heating unit is arranged externally with the cooling unit being arranged internally; and

FIG. 4 is a longitudinal sectional view of a special embodiment of the heating unit alone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 2, a reaction vessel 1 has, in known manner, a nest of tubes 6 arranged between two headers 4 and 5. Reaction vessel 6 includes an upper hood 2 and a lower hood 3. Immediately below upper header 4, the tube section communicates with a ring duct 7 and, immediately above lower header 5, the tube section communicates with a second ring duct 8. Ring ducts 7 and 8 surround vessel 1 circumferentially and concentrically.

On opposite sides of reaction vessel 1, thee two ring ducts 7 and 8 are connected the respective housings 9 and 10. Housing 9 contains a cooling unit or cooler 11 and housing 10 contains a heating unit or heater 12. Housing 9 has arranged therein a fan wheel 13 acting as a pump, and which is driven by a motor (not shown) arranged outside this housing. At the lower connection of housing 10, containing heating unit 12, with vessel 1, there is provided a combination shut-off and control element 14.

When the plant is in operation, circulation of the heat exchange medium, effected by fan wheel 13, takes place only between reaction vessel 1 and housing 9 of cooling unit 11. The heat exchange medium, cooled by cooling unit 11, enters the interior of reaction vessel 1 surrounding the nest of tubes 6 from all sides through lower ring duct 8, as indicated by the arrows in FIGS. 1 and 2. After the heat exchange medium flows upwardly of the nest of tubes 6, that is, in counterflow to the reaction medium conducted through the tubes from the top to the bottom, and has absorbed the heat released during the reaction process, the heat exchange medium enters upper ring duct 7 in all directions around the periphery of housing 1, and through duct 7 again arrives at housing 9 for cooling.

When the plant is started, or, if for any other reason, the reaction vessel 1 does not have the temperature necessary for the reaction process, the shut-off and control element 14 is opened and the heating unit 12 is activated. Then a larger or smaller partial amount of the heat exchange medium flows from lower ring duct 8 into housing 10, depending on the clear flow crosssection and, after being heated by heating unit 12, it flows into upper ring duct 7 in which it is mixed again with the other partial amount which is flown through the nest of tubes 6. The upward flow of the partial amount of the heat exchange medium passing through heating unit 12 is effected, apart from the increasing heat, by the pressure gradient between the lower and upper ring ducts 8 and 7, respectively, that is, substantially between the pressure side and the suction side of fan wheel 13.

In the embodiment of the invention shown in FIG. 3, a fan wheel 15 and cooling unit 16 are arranged, in a known manner, centrally inside reaction vessel 17, and the nest of tubes 18 is annular or ring-shaped. A guide tube 19 bounds the free central space of the nest of tubes 18 in its central region. Three ring-shaped or annular plates 20, 21 and 22 surround tube 19 at uniform axial spacings, and have flow cross-sections arranged alternately on their'outer and inner edges on different diameters. These plates, together with tube 19, serve, as indicated by the arrows, to guide the heat exchange medium circulating in reaction vessel 17.

In this case also, a heating unit 23 is arranged in a special housing 24 which is external to reaction vessel 17, and is connected to reaction vessel 17 at two points, namely at the lower and upper ends of the nest of tubes 18, by means of nipples 25, 26. In the upper nipple 26, there is arranged a combination shut-off and control element 27, to proportion the partial amount of the heat exchange medium circulating in the reaction vessel, heated if necessary by heating unit 12, in the same manner as in the embodiment shown in FIG. 1 but, in contrast to the embodiment shown in FIG. 1, at the upper region.

FIG. 4 illustrates a special design of an electric heating unit to be used in accordance with the invention. In this electric heating unit, protective tubes 31 extend from the top into housing 28, which latter is again connected, at two points at different levels and by nipples 29 and 30, to the reaction vessel which has not been illustrated in FIG. 4. Protective tubes 31 are closed at their bottom ends, and their open upper ends are sealed into a header or tube sheet 32. Into protective tubes 31, there are inserted electric heating rods 33 whose terminals 34 are arranged in a detachable and ventilated upper hood 35 of housing 28, protected against explosion. A slide valve 36, which can be moved up and down, serves to shut-off the inlet socket 29 or, if necessary, to adjust any desired flow cross-section. The heating unit also can be operated with any other suitable heat energy.

Special advantages of the invention reside particularly in that the heating unit is not only arranged externally of the reaction vessel but is also arranged in such a way that the rest of the plant, including the circulating and cooling unit of the heat exchange medium, can be operated completely independently of the heating unit. The heating unit thus can be, repaired or completely disassembled at any time without impairing the operability of the plant. In addition, there is no additional pressure loss in the circulating system of the heat exchange medium, because the latter passes in its full amount past the nest of tubes of the reaction vessel, with the heating unit shut-off, and with the heating unit connected, the partial amount passing by the heating unit need not pass by the nest of tubes.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a reaction vessel for carrying out exothermic chemical reactions, containing a nest of tubes, and having a heat carrier circulated therethrough in a cycle, by a pump, over the external surfaces of the tubes and conducted through a cooling device for extracting the heat absorbed by the heat carrier from the external surfaces of the tubes, the improvement comprising in combination, a heating unit arranged additionally external to said reaction vessel; means connecting said heating unit to said reaction vessel at two points at respective different pressures, for parallel connection of said heating unit with the normal circulating system of said heat carrier for selective circulation of at least a partial current of said heat carrier through said heating unit; and a regulating means in said connecting means controlling connection of said heating unit to said normal circulating system for regulating a partial current of said heat carrier through said heating unit.

2. In a reaction vessel, the improvement claimed in claim 1, in which said regulating means comprises a combined shut-off and control element at the inlet to said heating unit.

3. In a reaction vessel, the improvement claimed in claim 1, in which said regulating means comprises a combined shut-off and control element at the outlet of said heating unit.

4. In a reaction vessel, the improvement claimed in claim I, in which said heating unit is supplied with a heating fluid as a source of heat.

5. In a reaction vessel, the improvement claimed in claim 1, in which said heating unit is an electrically energized heating unit. 

1. In a reaction vessel for carrying out exothermic chemical reactions, containing a nest of tubes, and having a heat carrier circulated therethrough in a cycle, by a pump, over the external surfaces of the tubes and conducted through a cooling device for extracting the heat absorbed by the heat carrier from the external surfaces of the tubes, the improvement comprising in combination, a heating unit arranged additionally external to said reaction vessel; means connecting said heating unit to said reaction vessel at two points at respective different pressures, for parallel connection of said heating unit with the nOrmal circulating system of said heat carrier for selective circulation of at least a partial current of said heat carrier through said heating unit; and a regulating means in said connecting means controlling connection of said heating unit to said normal circulating system for regulating a partial current of said heat carrier through said heating unit.
 2. In a reaction vessel, the improvement claimed in claim 1, in which said regulating means comprises a combined shut-off and control element at the inlet to said heating unit.
 3. In a reaction vessel, the improvement claimed in claim 1, in which said regulating means comprises a combined shut-off and control element at the outlet of said heating unit.
 4. In a reaction vessel, the improvement claimed in claim 1, in which said heating unit is supplied with a heating fluid as a source of heat.
 5. In a reaction vessel, the improvement claimed in claim 1, in which said heating unit is an electrically energized heating unit. 